Improving the quality of soy sauce with mixed fermentation by Aspergillus oryzae

The koji was made by two kinds of Aspergillus oryzae with different characteristics respectively, and a soy sauce with better sensory quality was obtained with the fermentation of the mix koji. The results showed that the mixed fermentation of A. oryzae HT.AS1202 and HT.AS1205 at 1∶1 played the complementary role of the two strains in protease, pectinase, glutaminase and other enzymes. Compared with soy sauce fermented by single strain, the obtained soy sauce had lower total acid (1.94 g/100 ml), higher total sugar content (5.6 g/100 ml). The total nitrogen (1.80 g/100 ml) and amino acid nitrogen content (1.08 g/100 ml) met the national standard requirements of special grade soy sauce. The glutamate content was higher. The taste was characterized by outstanding umami, harmonious sour taste and moderate salty taste. There were 85 kinds of aroma components, compared with the soy sauce fermented by two single strains (79 kinds, 81 kinds), which not only retained the characteristics of soy sauce aroma, but also had light fruit fragrance.